Letting microorganisms break down “eternal chemicals”

Letting microorganisms break down “eternal chemicals”

Written by Saima S. Iqbal

A group of bacteria has been discovered that is adept at breaking the extremely strong carbon-fluorine bonds that give it its name. This discovery raises hopes that microbes may one day help remove these notoriously pervasive pollutants from the environment.

Approximately 15,000 chemicals commonly found in everyday consumer products such as pizza boxes, rain jackets, and sunscreen are recognized as per- and polyfluoroalkyl substances (PFAS). These chemicals can enter the body through drinking water or sludge-fertilized crops, and are already in the bloodstream of nearly everyone in the United States. Scientists have linked even low levels of chronic PFAS exposure to a myriad of health effects, including kidney cancer and thyroid disease. and ulcerative colitis.

Current methods of destroying PFAS require extreme heat or pressure and only work safely on filtered waste. Researchers have long wondered if bacteria could degrade chemicals in their natural environment, offering a cheaper and more scalable approach. But carbon and fluorine bonding occurs primarily in man-made materials, and PFAS have not been around long enough for bacteria to specifically evolve the ability to digest them. The new study is not the first to identify microbes that break down carbon-fluorine bonds, but it represents a step forward, says Northwestern, which is researching energy-efficient ways to chemically degrade PFAS. says university chemist William Dichtel.

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To identify a promising set of bacteria, the study authors screened several microbial communities living in wastewater. The research team reported that four strains of the Acetobacterium genus stood out. scientific progress. Each strain produced an enzyme that could digest caffeic acid, a natural plant compound that is roughly similar to some PFAS. This enzyme replaced certain fluorine atoms in PFAS with hydrogen atoms. “Transporter proteins” then carry the fluoride ion byproducts out of the single-celled microorganism, protecting it from damage. Over a three-week period, most strains break down the targeted PFAS molecules into smaller pieces that can be more easily broken down by traditional chemical means.

By directly targeting the bond between carbon and fluorine, acetic acid bacteria Bacteria partially digest perfluoroalkyl, a type of PFAS that most microorganisms cannot break down. Anyway, these are acetic acid bacteria This strain may only act on perfluoroalkyl molecules containing carbon-carbon double bonds adjacent to carbon-fluorine double bonds. These “unsaturated” perfluoroalkyl compounds serve as the building blocks for most large PFAS. They are produced by chemical manufacturers and also occur when PFAS are destroyed by incineration.

Scientists had previously demonstrated the existence of microorganisms such as: acidimicrobium sp. A6 strain can break carbon and fluorine bonds and completely degrade the two most ubiquitous perfluoroalkyls. However, this microorganism grows slowly and requires harsh environmental conditions to function. And researchers still don’t fully understand how this bacterial strain works.

of acetic acid bacteria The strain targets another PFAS group, and the team hopes to engineer the microbes to either improve efficiency or expand the possibility of reaching more perfluoroalkyls. Yujie Men, the study’s lead author at the University of California, Riverside, envisions microbes working best in combination with other approaches to breaking down PFAS. The range of chemical structures of these compounds means that “no single laboratory can solve this problem.”

Commercial use of this microorganism in the future will face many hurdles, including the rate of degradation and reproducibility outside the laboratory, but Meng is looking forward to seeing how far her team can push the technology. There is. “We’re paving the way,” she says with a laugh.